I'll offer a totally nonsensical solution that I would never advocate but does have a minor basis in reality.
Instead of bombing the Syrian base to smithereens with tomahawk missiles just air drop cases and cases of sarin gas down to the warring parties. Then let them have at it.
It would be a compromise aimed at appeasing all factions. Russia and Iran wouldn't complain since that's right up their alley. Hezbollah would be licking their chops since it would open the door to new opportunities. Israel would give it a big thumbs up. Gosh, it's a win/win all the way around.
Yes, it is a facetious idea. But one designed to point out we're only talking about a matter of degree here. Need some AK-47's - how many truckloads do you need? How about some MANPADS, you got it. Can I interest you in a little number we like to call "further measures" - Ahrar al-Sham gives it 5 stars.